If you are asked to find the 85th percentile, you are being asked to find

If you are asked to find the 85th percentile, you are being asked to find a data value associated with an area of 0.85 to its left. 
Percentile is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations fall. For example, the 30 th percentile is the value below which 20% of the observations may be found.